def insert_by

bend-mathlib@0.8.1.0 · perm.bend:67

import Base

67# Insertion into a list, generic comparator (structural, Base-only branching via Bool.pick).
68def insert_by(~A: Data, ~le: A -> A -> Bool, +x: A, xs: List<&2, A>) -> List<&2, A>:
69  match xs:
70    case Nil{}:
71      x <> Nil{}
72    case +y <> +t:
73      Bool.pick(List<&2, A>, le(x, y), x <> y <> t, y <> insert_by(~A, ~le, x, t))